Sunday, May 24, 2009

You are entering another dimension

Having less and less advantages to offer over home cinema, the movie studios have come up with a new plan to draw us to the movie theaters – 3D movies. With movies like Monsters and Aliens, Avatar, and many others, looks like 3D photography is going to be, if not successful, at least mainstream. Shooting in three dimensions may seem difficult, but in fact it is quite easy, and anyone with any camera can do it – even a phone camera.

Taking the shots is rather easy – all you have to do is realize the way the human vision works – each eye gives the brain a little different angle of the world, and the brain analyzes the difference to know the distance of everything from the viewer. If you compare the image seen by both eyes, by blinking with alternating eyes, you will notice that things are “shifted” left or right, and the close something is, the more it is shifted. To get this effect, all you have to do is take two pictures with your camera in a similar fashion – take one picture for the left eye, and another for the right one.

Taking a picture this way is simple, but the distance you move between the left and right image is important – if you move too little, the image will be flat, and if too much, the image might cause dizziness. To calculate the optimal distance, measure or estimate the distance between yourself and the closest object seen in the image, and divide that by 30. For example, if you see a bush in the front that is 15 feet away, then move 6 inches between the images. You should strive to keep the camera as level as possible between shots, and try to have the farthest object in the picture “move” as little as possible. This is easy if your Camera has a focus assist dot or cross onscreen – note where that cross touches, and after the move, aim the cross at the same point. This is not critical, as all these can be corrected later on, but it saves some trouble.

The biggest challenge of using this technique is that if something in the picture moves between the shots, it will appear weird in the composed 3D image. Taking pictures of inanimate objects or views is simple, but shooting people, animals or traffic is almost impossible (you can ask an adult to stay still, but that rarely works with a busy city intersection…). For this, the solution is to use two cameras, and take the photo simultaneously. It is important to have the cameras of the same model, or at least with the same lens, as different focal length will make the final images almost impossible to align without extensive graphics processing. Another option is to use a special 3D adapter, such as the one offered by Loreo. This adapter “splits” the image coming into the camera with a prism, creating the image at once. The main disadvantage to this is that the distance is fixed, so it is optimized for close-range shots. Recently some other equipment came to the market – the Minoru, which is a 3D webcam designed specifically for this. The quality is far from great, but this is nice to have. Soon, Fuji is planning on releasing a 3D digital camera, and I imagine many others are working on this as well.

Once the stereo pair is ready, the next challenge is to show the image correctly. The key here is to give each eye its own separate picture. The traditional way is using red-blue glasses. This is not perfect, as it distorts the color and if there are objects that are blue or red originally, they might appear “blinking”. Nevertheless, this is still the simplest way – download Stereo Photo Maker (http://stereo.jpn.org/eng/stphmkr/) and use it to combine the shots into one – the red/blue glasses are easily available online, usually for less than a buck for a paper-based pair, and there are higher quality glasses for little more. The software pictured below is another one, but all of them allow you to calibrate the picture position to achieve the best results.

And the end result (The Black Soldier monument in Boston):

Another way, which I won’t detail here, is to use Lenticular lens. This entails creating an interlaced image that combines both left and right images, and then placing a special sheet that contains thousands of narrow lens that project the slices into the eyes separately. This might be familiar to you from advertisements that have been popular recently. A Lenticular lens sheet costs about 5$ for a 4x6 image, and if you buy enough of them, it can reach less than a dollar. Unfortunately, Lenticular for personal use is still quite rare, so they are hard to find unless you are willing to spend 200$.